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Philips CD303 oddness
Philips CD303 oddness
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Old 3rd February 2015, 12:18 AM   #1
faulksy is offline faulksy  Australia
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Location: Melbourne
Default Philips CD303 oddness

A bit of background:

This player has been acting up for a while, white noise on left channel and an intermittent right channel, so i finally decided to have a look at it. Re-seating the DAC chips fixed the white noise but the right channel remained intermittent. The next step was replacing the electrolytic capacitors on the power supply board, no change. At this point I began replacing all the electrolytics in the player as at 30 yrs old there was a good chance at least one was dead. Whilst there I also touched up a few suspect looking solder joints around the MAB8410, SAA7011 and HEF4046(PLL controller) ICs.

The result of this is that the player will no longer read the TOC. Upon pressing play it spins up the disc, finds focus and then the program hangs. The disc will continue to spin with no sound until the player is switched off.

This is where it gets interesting. Putting the player into test mode by pressing the power and play buttons simultaneously shows that the basic functions are all working. After pressing the FWD, RWD and select keys in various combinations the player starts to play music. The program LEDs continue to cycle and the players functions, e.g FWD, RWD and track skip, can't be used. I should note that the original problems have been fixed, the audio on both channels is perfect.

My question is this, does anybody know why the machine will play music while in test mode but not under normal operation?
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Old 3rd February 2015, 05:31 PM   #2
stephensank is offline stephensank  United States
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I believe this is the generation with the soldered-through ground points on the servo board and elswhere. If all of these have not been resoldered, strange things can happen. These are the places where the top-side ground plane solder through to bottom-side traces.
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Old 3rd February 2015, 11:32 PM   #3
Willi Studer is offline Willi Studer  Serbia
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Test mode in CDM0 and CDM1 machines includes a step (usually the last) in which the laser pickup will read out the TOC and begin following the track. Music will also become audible. This step is used for checking the radial control circuit and clock regeneration in PLL circuit. The difference from the normal playback is that in test mode the microprocessor will not intervene in tracking and error correction. That means that any bounce or mechanical vibration will tilt the pickup from playback irrecoverably.
In normal operation mode, check the EFAB signal on MAB8410 which should be low. If it is high, it means the microprocessor has detected an uncorrectable error and/or is confused.
A default checkup list of possible faults and errors after working on a piece of electronics: check for solder joints, accidentally reversed polarities and, as stephensank pointed out, through-PCB solder bridges.
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Old 5th February 2015, 12:40 PM   #4
faulksy is offline faulksy  Australia
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Join Date: Jul 2008
Location: Melbourne
Thanks guys for the replies. The machine is old enough to not have double sided boards so does not have any through hole grounds.

Looking at the service manual it does not show or mention the EFAB signal, which pin should I be looking for this on?

Studying the decoder board revealed a couple of bridged solder joints around the MAB8410, I have fixed these but this has not remedied the problem. After fixing the solder joints I placed a brand new MAB8410 with the correct program code into the socket in case it the original was damaged but there is still no change.

as the test mode bypasses the error correction should i start looking at the CX7933, CX7934 and CX7935 chips? This model has the SOPHI board instead of the SAA7020 for error correction.
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Old 3rd July 2018, 11:28 AM   #5
Simtu is offline Simtu  England
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Join Date: Feb 2012
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Hi.

I didn't want to start a new thread but thought "cd303 oddness" summed up my issue nicely.

I recently bought a spares or repair cd303 on EBay. It was non working (powered up but wouldnt read the TOC) so I replaced all of the electrolytics in the power supply and on the cdm0 board as a starting point. Player would then at least spin the disc, making a rhythmic ticking noise as the laser oscillates back and forth at the inner home position.

I then tried raising the motor spindle a tad. This was successful - the player now reads the TOC, the display lights up and the music plays.

The only problem is that it will only work when the greenish/grey protection plate beneath the cdm0 is left off as well as the main bottom plate of the outer enclosure. I find that if I tweek the spindle adjustment, I can get the player to work again. As soon as I reassemble the metalwork, it stops again. The only cure is to disassemble the player again and re-tweek the spindle.

I have played it like this for several hours without fault. It will play any disc I throw at it without skipping or causing any problems - but only when the casework is left off.

I have looked to see whether the torx screws are touching anything or causing shorts but I cannot find anything.

Does anyone have any ideas?

Thanks, Simon
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Old 18th July 2018, 02:02 PM   #6
Simtu is offline Simtu  England
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Does anyone have any ideas?
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